Many women who get chemotherapy to treat breast cancer say they have problems remembering, thinking, and concentrating during and after treatment. These problems are commonly called “chemo brain” or “chemo fog” – doctors call these issues “cognitive impairment” or “cognitive problems.”

Women who’ve received chemotherapy to treat breast cancer have long complained about chemo brain. Still, some doctors question whether chemo brain actually exists. Others think the condition is related to hormonal therapy or depression and anxiety instead of chemotherapy.

In this Belgian study, the researchers looked at three groups of women:

18 women diagnosed with early-stage breast cancer who were scheduled to receive chemotherapy

16 women diagnosed with early-stage breast cancer who weren’t going to have chemotherapy

17 women who hadn’t been diagnosed with breast cancer and were considered healthy

Each group of women did multitasking assignments while the researchers did functional MRI scans of their brains. A functional MRI (fMRI) scanner allows doctors to measure how active certain areas of the brain are when specific tasks are being done.

Each group of women did the same multitasking assignments and each group was scanned twice:

1 to 2 weeks before chemotherapy started (the two groups who weren’t getting chemotherapy were scanned at the same time)

4 to 6 months after chemotherapy ended (the two groups who didn’t get chemotherapy were scanned at the same time)

The researchers didn’t see any differences in brain activity between the three groups of women after the first fMRI scan.

The second fMRI scan showed lower levels of brain activity in the cingulate cortex area of the brain while multitasking in the women who were treated with chemotherapy, but not in the two other groups. The women diagnosed with breast cancer who didn’t receive chemotherapy and the healthy women had the same level of brain activity in the second scan as they did in the first.

The cingulate cortex is involved with emotion formation and processing, learning, and memory. It’s also believed to play an important role in depression.

About the same time the second fMRI scan was done, the women who had been treated with chemotherapy were reporting that they were having more problems thinking, remembering, and concentrating.

The researchers aren’t sure exactly how chemotherapy may be causing this decreased brain activity. It could be that chemotherapy may be damaging some brain cells or making it harder for different regions of the brain to communicate with each other. More research is needed to figure out exactly how chemotherapy is affecting brain activity.

It’s interesting to know that of the women diagnosed with breast cancer in the study, 14 of the women who received chemotherapy and 12 of the women who didn’t get chemotherapy were treated with the hormonal therapy medicine tamoxifen. Other research has suggested that hormonal therapy might actually be the cause of chemo brain, not chemotherapy. But in this study, hormonal therapy seemed to have no effect on brain activity. Also, the women who were taking tamoxifen but weren’t treated with chemotherapy didn’t report an increase in cognitive problems.

The good news is that most women who have memory and thinking problems during breast cancer treatment recover and are able to remember and think clearly after treatment is done. Still, a small number of women continue to have problems for a year or more after treatment ends.

If you’ve been diagnosed with breast cancer and are having thinking and memory problems, there are things you can do to help yourself. Read our page on Memory Loss or more information.

Stay tuned to Breastcancer.org Research News for the latest information on chemo brain and its causes.